Browsing by Author "Rong, Yu"

Now showing 1 - 8 of 8
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    A Universe of ultradiffuse galaxies: theoretical predictions from ΛCDM simulations
    (2017) Rong, Yu; Guo, Qi; Gao, Liang; Liao, Shihong; Xie, Lizhi; Puzia, Thomas H.; Sun Shuangpeng; Pan, Jun
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    Intrinsic Morphology of Ultra-diffuse Galaxies
    (IOP PUBLISHING LTD, 2020) Rong, Yu; Dong, Xiao Yu; Puzia, Thomas H.; Galaz, Gaspar; Sanchez Janssen, Ruben; Cao, Tianwen; van der Burg, Remco F. J.; Sifon, Cristobal; Pina, Pavel E. Mancera; Marcelo, Mora; D'Ago, Giuseppe; Zhang, Hong Xin; Johnston, Evelyn J.; Eigenthaler, Paul
    With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z similar to 0.020-0.063) galaxy clusters and 84 UDGs in two intermediate-redshift (z similar to 0.308-0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert, i.e., the underlying shapes of UDGs are purely prolate (C = B < A), we find that the data favor the oblate-triaxial models (i.e., thick disks with C < B less than or similar to A) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are related to their stellar masses/luminosities, environments, and redshifts. First, the more luminous UDGs have puffier morphologies compared with the less luminous counterparts; the UDG morphologic dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs); in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories; they may differ not only in size. Second, the UDGs with smaller clustercentric distances are more puffed up, compared with the counterparts with larger clustercentric distances; in combination with the UDG thickness dependence on luminosity, the puffier morphologies of UDGs with high luminosities or located in the denser environments are very likely to be attributed to tidal interactions with massive galaxies. Third, we find that the intermediate-redshift UDGs are more flattened, compared with the low-redshift counterparts, which plausibly suggests a "disky" origin for the high-redshift, newly born UDGs.
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    Lessons on Star-forming Ultra-diffuse Galaxies from the Stacked Spectra of the Sloan Digital Sky Survey
    (2020) Rong, Yu; Zhu, Kai; Johnston, Evelyn J.; Zhang, Hong-Xin; Cao, Tianwen; Puzia, Thomas H.; Galaz, Gaspar
    We investigate the on-average properties for 28 star-forming ultra-diffuse galaxies (UDGs) located in low-density environments, by stacking their spectra from the Sloan Digital Sky Survey. These relatively isolated UDGs, with stellar masses of log(10) (M-*/M-circle dot) similar to 8.57 +/- 0.29, have the on-average total stellar metallicity [M/H] similar to -0.82 +/- 0.14, iron metallicity [Fe/H] similar to -1.00 +/- 0.16, stellar age t(*) similar to 5.2 +/- 0.5 Gyr, alpha-enhancement [alpha/Fe] similar to 0.24 +/- 0.10, and oxygen abundance 12+log(O/H) similar to 8.16 +/- 0.06, as well as central stellar velocity dispersion 54 +/- 12 km s(-1). On the star formation rate versus stellar mass diagram, these UDGs are located lower than the extrapolated star-forming main sequence from the massive spirals, but roughly follow the main sequence of low-surface-brightness dwarf galaxies. We find that these star-forming UDGs are not particularly metal-poor or metal-rich for their stellar masses, as compared with the metallicity-mass relations of the nearby typical dwarfs. With the UDG data of this work and previous studies, we also find a coarse correlation between [Fe/H] and magnesium-element enhancement [Mg/Fe] for UDGs: [Mg/Fe] similar or equal to -0.43(+/- 0.26) [Fe/H] -0.14(+/- 0.40).
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    SDSS-IV MaNGA: a distinct mass distribution explored in slow-rotating early-type galaxies
    (OXFORD UNIV PRESS, 2018) Rong, Yu; Li, Hongyu; Wang, Jie; Gao, Liang; Li, Ran; Ge, Junqiang; Jing, Yingjie; Pan, Jun; Fernandez Trincado, J. G.; Valenzuela, Octavio; Aquino Ortiz, Erik
    We study the radial acceleration relation (RAR) for early-type galaxies (ETGs) in the SDSS MaNGA MPL5 data set. The complete ETG sample show a slightly offset RAR from the relation reported by McGaugh et al. (2016) at the low-acceleration end; we find that the deviation is due to the fact that the slow rotators show a systematically higher acceleration relation than the McGaugh's RAR, while the fast rotators show a consistent acceleration relation to McGaugh's RAR. There is a 1 sigma significant difference between the acceleration relations of the fast and slow rotators, suggesting that the acceleration relation correlates with the galactic spins, and that the slow rotators may have a different mass distribution compared with fast rotators and late-type galaxies. We suspect that the acceleration relation deviation of slow rotators may be attributed to more galaxy merger events, which would disrupt the original spins and correlated distributions of baryons and dark matter orbits in galaxies.
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    SDSS-IV MaNGA: Cannibalism Caught in the Act-On the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies
    (2022) Hsu, Yun-Hsin; Lin, Yen-Ting; Huang, Song; Nelson, Dylan; Rodriguez-Gomez, Vicente; Lai, Hsuan-Ting; Greene, Jenny; Leauthaud, Alexie; Aragon-Salamanca, Alfonso; Bundy, Kevin; Emsellem, Eric; Merrifield, Michael; More, Surhud; Okabe, Nobuhiro; Rong, Yu; Brownstein, Joel R.; Lane, Richard R.; Pan, Kaike; Schneider, Donald P.
    Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the universe, is still not well understood. Several independent measurements have indicated a slower mass growth rate than predictions from theoretical models. We attempt to resolve the discrepancy by measuring the frequency of BCGs with multiple cores, which serve as a proxy of the merger rates in the central region and facilitate a more direct comparison with theoretical predictions. Using 79 BCGs at z = 0.06-0.15 with integral field spectroscopic data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, we obtain a multiple-core fraction of 0.11 +/- 0.04 at z approximate to 0.1 within an 18 kpc radius from the center, which is comparable to the value of 0.08 +/- 0.04 derived from mock observations of 218 simulated BCGs from the cosmological hydrodynamical simulation IllustrisTNG. We find that most cores that appear close to the BCGs from imaging data turn out to be physically associated systems. Anchoring on the similarity in the multiple-core frequency between the MaNGA and IllustrisTNG, we discuss the mass growth rate of BCGs over the past 4.5 Gyr.
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    The formation and evolution of massive galaxies
    (2021) Jing, Ying-Jie; Rong, Yu; Wang, Jie; Guo, Qi; Gao, Liang
    The discovery of massive galaxies at high redshifts, especially the passive ones, poses a big challenge for the current standard galaxy formation models. Here we use the semi-analytic galaxy formation model developed by Henriques et al. to explore the formation and evolution of massive galaxies (MGs, stellar-mass M-* > 10(11) M-circle dot). Different from previous works, we focus on the ones just formed (e.g. just reach similar or equal to 10(11) M-circle dot). We find that most of the MGs are formed around z = 0.6, with the earliest formation at z > 4. Interestingly, although most of the MGs in the local Universe are passive, we find that only 13% of the MGs are quenched at the formation time. Most of the quenched MGs at formation already host a very massive supermassive black hole (SMBH) which could power the very effective AGN feedback. For the star-forming MGs, the ones with more massive SMBH prefer to quench in shorter timescales; in particular, those with M-SMBH > 10(7.5) M-circle dot have a quenching timescale of similar to 0.5 Gyr and the characteristic M-SMBH depends on the chosen stellar mass threshold in the definition of MGs as a result of their co-evolution. We also find that the "in-situ" star formation dominates the stellar mass growth of MGs until they are formed. Over the whole redshift range, we find the quiescent MGs prefer to stay in more massive dark matter halos, and have more massive SMBH and less cold gas masses. Our results provide a new angle on the whole life of the growth of MGs in the Universe.
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    The Next Generation Fornax Survey (NGFS). III. Revealing the Spatial Substructure of the Dwarf Galaxy Population Inside Half of Fornax's Virial Radius
    (2018) Órdenes Briceño, Yasna; Eigenthaler, Paul; Taylor, Matthew A.; Puzia, Thomas H.; Alamo-Martinez, Karla; Ribbeck, Karen X.; Munoz, Roberto P.; Zhang, Hongxin; Grebel, Eva K.; Ángel Ángel, Simón Andrés; Cote, Patrick; Ferrarese, Laura; Hilker, Michael; Lancon, Ariane; Mieske, Steffen; Miller, Bryan W.; Rong, Yu; Sanchez-Janssen, Ruben
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    The Next Generation Fornax Survey (NGFS). IV. Mass and Age Bimodality of Nuclear Clusters in the Fornax Core Region
    (2018) Órdenes Briceño, Yasna; Puzia, Thomas H.; Eigenthaler, Paul; Taylor, Matthew A.; Munoz, Roberto P.; Zhang, Hongxin; Alamo-Martinez, Karla; Ribbeck, Karen X.; Grebel, Eva K.; Ángel Ángel, Simón Andrés; Cote, Patrick; Ferrarese, Laura; Hilker, Michael; Lancon, Ariane; Mieske, Steffen; Miller, Bryan W.; Rong, Yu; Sanchez-Janssen, Ruben